Constant band width receiver



May 12, 1936. J. L. BONANNO CONSTANT BAND WIDTH RECEIVER I Filed Aug. 20, 1929 I 70 SUCCEE'D/NG .5746! IE 5 O J a NVENTOR PH L. BONANNO.

ATTORNEY.

Patented May 12, 1936 PATENT OFFICE CONSTANT BAND WIDTH RECEIVER Joseph L. Bonanno, Forest Hills, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application August 20, 1929, Serial No. 387,148

10 Claims.

My present invention relates to couplings for radio circuits, and, more particularly, to a method of, and means for, maintaining a constant band width in a radio receiver.

When employing either'pure magnetic or capacity coupling between radio circuits, it is found that the coupling increases more rapidly at higher resonant frequencies than is desired. It has been determined, however, that by combining magnetic and capacity coupling in proper phase relation the capacity coupling can be made to diminish the total coupling so that an improved resonance curve results at the high fre quency end of the range.

Now, I have devised a method of obtaining a constant coupling between a pair of radio circuits, or, generically considered, a method of obtaining any desired rate of variation of coupling, as the resonance frequency is varied, and this method is one of the main objects of my present invention. 1 Another important object of the invention is to provide a radio receiver comprising a plurality of circuits tuned by means of a gang of condensers, in which the shielding effect of an element, usually a rotor, is employed to vary the inter-stator capacity of adjacent end stator plates of adjacent condensers.

Another important object of the invention is to provide a radio receiver including a plurality of tunable circuits, a gang of condensers for tuning the circuits, said gang including a rotatable plate between a predetermined pair of stators, the capacity between the stators being thereby variable and controlled by therotor to secure a predetermined coupling between said circuits at any frequency.

Still another object of the invention is to provide a radio receiver including a plurality of circuits tuned by a gang of condenser groups, the gang having at least one grounded rotor plate between each pair of condenser groups, the rotor plate being designed in any predetermined shape to secure a desired variation of capacity coupling between said tuned circuits throughout the frequency range whereby a predetermined resonance curve is secured over said range.

Other objects of the invention are to improve generally the simplicity and efiiciency of tuned circuit couplings, and to provide a coupling for radio circuits which is reliable in operation; follows a predetermined law of variation through a given frequency range, and is economical to manufacture. V

" The novel features which I believe to be characteristic of my invention are set forth in particularity in the appended claims, the invention itself, however, as to both its organization and method of operation will best be understood by reference to the following description taken in connection with the drawing in which I have indicated diagrammatically several circuit organizations whereby my invention maybe carried into effect.

In the drawing, 10

Fig. 1 shows schematically a circuit employing combined transformer and variable capacity coupling,

Fig. 2 is a diagrammatic view of a circuit solely employing variable capacity coupling,

Fig. 3 is a sectional view of a gang condenser embodying one form of the present invention.

Fig. 3a shows a side elevation of the plate P, in isometric,

Fig. 4 is of a sectional view of a gang con-' denser embodying a modified form of the invention,

Fig. 4a. is a side elevation looking in the direction of the arrow in Fig. 4.

Referring to the accompanying drawing in which like characters of reference indicate the same parts in the different figures, there is shown in Fig. 1 a receiving circuit including combined transformer and capacity coupling between tuned radio frequency stages. A grounded antenna 30 circuit A, G is coupled, as at M, to a conventional radio frequency amplifier, the output of the latter being coupled, as at M1, to the input circuit of the succeeding stage. r

The output circuit of the first radio stage includes an inductance L1, tuned by a variable condenser C1, the latter having its rotor plates R1 grounded. The secondary coil L2 of the transformer coupling M1 is tuned by a variable condenser C2, the latter being connected in parallel with the coil, the rotors R2 of the condenser also being grounded. The rotor plates R1 and R2 of the two condensers are mounted on a-common shaft, in practice.

As explained, heretofore, by properly combining the capacity coupling Cc, between the end stator plates of adjacent condensers. C1 and C2, and the transformer coupling M1, in the proper phase relation, the capacity coupling Cc can be made to decrease the total coupling so that an improved shape of resonance curve results at the high frequency end of the working range. In other words, the capacity coupling and magnetic coupling Mi are to be combined in'opposite phase. The coils L1 and L2 are poled, 'of' course, for

" r b per phase. It follows, then, that with a given set of coils one has merely to pole, or connect,

7 the coils relatively to eachother in the sense grounded antenna circuit A, G coupled, as at to a conventional radio frequency amplifier, the 7 output ofthe latter being coupled to the input of the succeeding stage solely by capacitive means. r

The coils L1 and L2 are the inductances of the coupled stages, and the condensers C1 and C2 are 1 their respective tuning capacities. No magnetic coupling exists between the coils, the shields T1, "and T2 being shown indotted lines, coupling being accomplished solely by the'capacity Cc.' It is understood, of course, that the rotors of C1 and C2 are mountedon a common shaft, and that the *capacity Cc represents the inter-stator capacity of the end stator plates of the two condensers C1 and 02, Variation of Co beingsecured by a rotat "able plate mounted on the said common shaft. In Fig. ,3, there is shown a structural embodiment of the capacities C1, C5, C2. The stators S1 and S of the condensers C1 and C2 are supported on insulation spacers K. The casing I of the condensers is of a bath-tub shape, and is made ,Of metal. A metallic rotor shaft 2 is supported in bearings 3, 3', andis actuated by a knob 4.

' Theroto-r plates R1 and R2 mesh with their respective stators S1 and S2, the former being afiixed to the shaft 2 for rotation therewith, in the usual manner. Between the end stator plates of the two sectionsof the gang condenser, there is disposed .a metallic rotor P, which is grounded through the bath-tub shell I because itisdirectly connected to the metallic shaft 2. V 7

Thus, in Fig. 3, there is disclosed a gang condenser of thelg'rounded rotor type, the capacity between'the stators of the condenser groups being equal to, or greater than, the maximum required at any frequency. This coupling capacity Co is decreased to suit the circuit requirements, at various frequencies, by interposing a grounded, vari- {able shield, i. e. the grounded rotor plate P,

circular, then a contour for the plate P, as shown in Figure Set will result in a decrease incapacity between plates 9 and ID as the plates R1 and R2 mesh with stator plates S1 and S2, assumingthat the plate P moves in the direction of the arrow,

shpwnin Figures 3 and 3a, as the plates, R1 and R2 move into mesh and in theopposite direction. In Fig; 4,1 have showna second form of' gang condenser, embodying the present invention, the

"l normal coupling between stators being-practi- 'cally zero, due to the grounded" metallic partiw tion 5, between the end stators 9 and Ill. The

, construction of this gang condenser is practically value, bythe metallic rotor plates P1 and P2, mounted on the shaft 2.

Between the end stator of each gang section and the partition 5,'is disposed a rotor plate. Thus, plates P1 and P2 are provided for varying the coupling capacity between the end stators of the gang sections. The plates P1 and P2 connected by sleeve 6' are mounted on an insulating bushing 6, the bushing being concentric with the rotor shaft 2. In Figure'4a is shown the relation between the areas of the partition 5, the plates P1 and P2, and the stator plates 9 and I0.

Plates P, P1 and P2 can be given any desired shape, the latter being such that the plates cooperate with the exposed stator end plates to vary the capacity Cc, according to any desired law. In Fig. 4, practically all of the capacity coupling is determined by the plates P1 and P2, because'of It will, of course, be'

the shielding partition 5. understood that any predetermined combinations of variable and fixed capacitances may be used to secure the desired coupling capacity at any frequency.

It is to be understood that the condensers shown in Figs. 3 and 4 may be used interchangeably in either of the circuits shown in Figs. land pling, the latter being obtained, as a modification r of the first mode, by inter-stator capacity controlled by'a plate rotating with the gang condenser shaft, but insulated therefrom, it being particularly noted that the two modes of varying capacitive coupling are equally adapted for use with either of the said two systems.

While I have indicated and described several systems for carrying my invention into effect,

it will be apparent to one skilled in the art that my invention is by no means limited to the particular organizations shown and described, but that many modifications in the circuit arrangements, as well as in the apparatus employed, may be made without departing from the scope of my invention as set forth in the appended claims.

What I claim is:

1. A high frequency network comprising a pair of resonant oscillation circuits having fixed inductors with substantially zero mutual inductances between them, variable tuning condensers connected to said inductors having a mutual capacitance between stator elements thereof, said capacitance providing electrostatic coupling between said circuits, a single means for simultaneously adjusting said tuning condensers, and means controlled by said single adjusting means for varying said electrostatic coupling between the resonant circults.

2. The invention defined in the preceding claim wherein the electrostatic coupling means is simultaneously varied with the tuning ,in a predetermined manner. a

3. The invention defined in claim 1 wherein the electrostatic coupling means comprises an earthed rotor plate which is mounted upon the single adjusting means and which is adapted to operate as a variable shielding member between ill stator elements providing the aforesaid mutual capacitance.

' 4. A high frequency network comprising a pair of resonant oscillation circuits having fixed inductors, variable tuning condensers connected to said inductors having a mutual capacitance between stator elements thereof, said capacitance providing electrostatic coupling between said circuits, a single means for simultaneously adjusting said tuning condensers, and means controlled by said single adjusting means for varying said electrostatic coupling between the resonant circuits, said electrostatic coupling means comprising an earthed rotor plate which is mounted upon the single adjusting means and which is adapted to operate as a variable shielding member between stator elements providing the aforesaid mutual capacitance.

5. A high frequency network comprising a pair of resonant oscillation circuits having fixed inductors, means for shielding said inductors whereby there exists substantially zero mutual inductance between them, variable tuning condensers connected to said inductors having a mutual capacitance between stator elements thereof, said capacitance providing electrostatic coupling between said circuits, a single means for simultaneously adjusting said tuning condensers, and means controlled by said single adjusting means for varying said electrostatic coupling between the resonant circuits.

6. A high frequency network comprising a pair of oscillation circuits, each provided with a variable condenser having rotors and stators, a common mechanical control for the condenser rotors of both circuits, and means operatively connected with the common control to variably adjust the capacity coupling provided between adjacent end stators of said condensers, said capacity coupling providing the sole energy transfer path between said oscillation circuits.

7. A high frequency network comprising a pair of oscillation circuits, each provided with a variable condenser having rotors and stators, a common mechanical control for the condenser rotors of both circuits, and means operatively connected with the common control to variably adjust the capacity coupling provided between predetermined stators of said condensers, said capacity coupling providing the sole energy transfer path between said oscillation circuits, an inductance coil included in each of said circuits, said two coils having substantially zero mutual inductive coupling between them.

8. A high frequency network comprising a pair of oscillation circuits, each provided with a. variable condenser having rotors and stators, a common mechanical control for the condenser rotors of both circuits being adjacent each other to function as a tuning unit, and means operatively connected with the common control to variably adjust simultaneously with tuning the capacity coupling provided between predetermined stators of said condensers, said capacity coupling providing the only energy transfer path between said oscillation circuits, an inductance included in each oscillation circuit, and means for preventing magnetic coupling between said inductances.

9. A high frequency network comprising a pair of oscillation circuits, each provided with a variable condenser having rotors and stators, a common mechanical control for the condenser rotors of both circuits being adjacent each other to function as a tuning unit, and means operatively connected with the common control to variably adjust the capacity coupling provided between predetermined stators of said condensers, said capacity coupling providing an energy transfer path between said oscillation circuits, said coupling adjusting means comprising an electrostatic shield interposed between said predetermined stators and movable relatively thereto upon adjustment of said common control.

10. A high frequency network comprising a pair of oscillation circuits, each provided with a variable condenser having rotors and stators, a

common control shaft for the condenser rotors of both circuits being adjacent each other to function as a tuning unit, and means operatively connected with said control shaft to variably adjust the capacity coupling provided between predetermined stators of said condensers, said capacity coupling providing an energy transfer path between said oscillation circuits, an electrostatic shield disposed between the said predetermined stators, said coupling adjusting means comprising a conductive element electrostatically coupling said predetermined stators, said element being insulatingly mounted upon said common control shaft.

JOSEPH L. BONANNO. 

